Thermal accelerometers are known that comprise an enclosure in which a central filament is disposed that is connected to a power supply member delivering electricity, and that lies between two detector filaments connected to a member for comparing the temperatures of the detector filaments. When the accelerometer is used for measuring the acceleration to which the vehicle carrying the accelerometer is subjected, the central filament is raised to a high temperature by using a direct current (DC) power supply. The temperature gradient about the central filament is a function of the acceleration to which the accelerometer is subjected. Measuring a temperature difference between the detector filaments thus makes it possible to calculate the acceleration to which the accelerometer is being subjected. To ensure that the electronics performing the calculation operates correctly, it is known to power the detector filaments with alternating current (AC). The central filament is not concerned by this accuracy constraint, which explains why it can be powered with DC.
In order to increase the speed and the accuracy with which acceleration is determined, proposals are made in document FR-A-2 817 351 to dispose reaction filaments adjacent to the detector filaments, which reaction filaments are connected to power supply members delivering the reaction filaments with electrical reaction currents in the form of same-sign DC or of pulses. Under such circumstances, a reaction filament is powered in such a manner as to balance the temperature difference between the detector filaments, and acceleration measurement is performed by measuring the power needed to achieve such balance.
In both cases, unexplained measurement errors have been observed under conditions where the accelerometer was subject to the same accelerations.